No login secreen on Jessie

[Markos <markos@c2o.pro.br>]

Hi,

I just installed Debian 8.1.0 jessie with CD 1 and CD 2 on a old desktop 
with the configuration:

Motherboard: ECS Elitegroup 848P-A (v 1.0)
Processor: Pentium 4 (3GHz),
2GB DDR
HD SATA Seagate Barracuda 160GB
Video: nVidia NV34 [GeForce FX 5200]
Network: Realtek RTL-8139/8139C/8139C+
Audio: Intel 82801EB/ER (ICH5/ICH5R) AC'97

I had problems during installation and installed just the basic system.

Later I installed gnome(apt-get install gnome), but after the boot does 
not appear the login screen, just a black screen.

How can I find the reason of the problem?

I can log just on text mode with Ctrl+Alt+Fn

Thanks,
Markos